As a result of traditional selective breeding methods, milk production in dairy cows far exceeds the requirements of the newborn calf. Because of udder size, position, and anatomic configuration for rapid removal of large volumes of milk, the mammary glands of dairy cows are especially prone to injury and infection. In particular, mastitis, an infection of the mammary gland, is common in milking dairy cows, sheep, goats, and other milk-producing animals.
Clinically, mastitis typically produces heat, swelling, tenderness and possible deformation of the udder. Although the milk from a mastitic udder is generally safe for human consumption, a major concern is the cost to producers. Mastitis causes a decrease in the amount and quality of milk produced by the infected cow. With decreased quality, the price obtained for the milk likewise decreases. In some instances, depending on the level of infection, the milk is completely unsuitable. When this occurs, there are more white blood cells, also called somatic cells, secreted into the milk. Milk having a somatic cell count (SCC) of over 750,000/ml is considered unsaleable in the U.S. Other countries have different acceptable levels of somatic cell count.
In most modern milking operations, the milk from all cows being milked at a facility is combined together for sale. Unfortunately, milk from one mastitic cow may sufficiently taint the quality of the entire volume of milk, and thus decrease the price obtained for the entire volume, possibly rendering unsaleable the entire volume of milk if the level of infection is sufficiently high.
A common test for the presence of mastitic infection is the California Mastitis Test (CMT). This test, however, is a manual test that takes several minutes and is very subject to interpretation. Electrical conductivity testing of the milk is also a common test used for the presence of mastitic infection. This method of mastitis detection, however, has not been reliable.
What is desired is a fast, cost efficient method for determining the presence, and extent, of any mastitis infection, prior to the milk from an infected cow being mixed with higher quality milk.